1. Field of the Invention
The present invention relates to an electroconductive (hereinafter, also referred to as “conductive”) bonding material comprising an electroconductive particles ingredient, an epoxy resin ingredient and an epoxy resin-hardening ingredient, a method for producing an electric/electronic circuit, as well as an electric/electronic device having such an electric/electronic circuit.
2. Description of Related Art
In the field of producing electric/electronic circuits, an electroconductive bonding material, i.e. an electroconductive adhesive is widely used for the purposes of mounting electric/electronic components (hereinafter, also collectively referred to as “electric components”) onto a circuit board and the purposes of forming conductor pattern on a circuit board. The electroconductive adhesives, which are used in the field of mounting the electric components, basically having a composition comprising a resin composition as a binder and conductive particles of such as metallic particles which are dispersed in the resin composition. The conductive adhesives, wherein the resin composition has a paste-like form, are referred to as the conductive paste.
Such resin composition contains a resin-hardening ingredient, which makes the resin composition harden by being subjected to a condition, e.g. by being subjected to a predetermined temperature condition. When a conductive adhesive is subjected to a predetermined temperature condition, the resin composition therein volumetrically shrinks while hardening, so that the volume of the resin composition as a whole decreases. As a result, the conductive particles which were dispersed in the resin composition come to contact one another and form a continuous conductive path through the hardened conductive adhesive.
As an example of such conductive adhesives, there is an epoxy-based conductive adhesive composition which contains an epoxy resin as the resin composition, a hardening agent for hardening the epoxy resin, and metallic particles such as silver or nickel as the conductive ingredient. The conductive adhesive compositions of such type hardens generally by being heated to a temperature of 120 degree centigrade or more.
Recently, electric components having lower heat resistance property are frequently used in connection with the advancement of the functions of electric components. Accordingly, a conductive adhesive (i.e. a bonding material for mounting) which hardens at a lower temperature is highly required. Further, considering the operability at work sites, preservation stability for a period from several days to several weeks in the adhesive component state is also required for a one-component adhesive composition as mentioned in the above.
Intending to prepare a conductive adhesive paste having lower hardening temperature, applying one-component type epoxy resin composition having a low hardening temperature, which has been known as an adhesive material, to a conductive paste is examined. For example, a resin composition containing an epoxy resin, a thiol compound as the hardening agent and a latent hardening promotor of solid dispersed type is known as an adhesive (Patent Document 1). Furthermore, aiming to improve preservation stability, a conductive paste containing a borate ester compound in addition to the above composition is proposed (Patent Document 2).    [Patent Document 1] Japanese Patent Kokai Publication No. 211969/1994    [Patent Document 2] Japanese Patent Kokai Publication No. 2000-230112